Area Forecast Discussion
Issued by NWS Wilmington, NC

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000 FXUS62 KILM 161748 AFDILM Area Forecast Discussion National Weather Service Wilmington NC 148 PM EDT Wed Aug 16 2017 .SYNOPSIS... Summertime heat and humidity will build across the area through Friday. Showers and thunderstorms will be on the increase during the weekend as a cold front approaches from the north. This front may stall in close proximity early next week. && .NEAR TERM /THROUGH TONIGHT/... As of 1015 AM Wednesday...Another warm and humid day is expected across the area, as temperatures this morning are already in the mid 80`s. Expect temperatures to climb into the lower 90`s by this afternoon, and this along with dewpoints, do expect heat indices to rise above 100 across the area. With that said, a Heat Advisory has been raised for all SC counties in the CWA, with the addition of the inland portions of Brunswick county and Columbus county for the afternoon hours. Latest observations continue to indicate a weak trough situated across our area this morning, and this along with the afternoon seabreeze and the piedmont trough, do expect isolated to scattered showers and thunderstorms to develop today, typical to the summertime popcorn type convection. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 300 AM Wednesday...The center of warm high pressure will be positioned across portions of FL and the Southeast states Thu into Fri. As a longwave trough progressively digs across the eastern third of the nation late Fri and Fri night, it will help drive a surface cold front to the SE. This front should reach central portions of central North Carolina and the upstate of South Carolina by Sat morning. 850 mb temps will be 19-21 deg C during this period. This will allow high temps to rise into the lower to mid 90s. These temps are fairly typical for the later half of Aug. However, dewpoints will be in the mid and upper 70s with perhaps an 80 deg dewpoint for portions of the coast. This will make it uncomfortable to be outdoors as afternoon heat index values will be near or above 105 and as high as 109 deg both Thu and Fri. These conditions will likely require a Heat Advisory. The nights will be in the muggy mid and upper 70s. As for the risk for convection, it will be hit or miss Thu with the seabreeze being the primary impetus for convection along the coast and the Piedmont Trough for areas further inland. Morning and early afternoon convection that does develop along the coast should tend to migrate inland and away from the beaches as the afternoon progresses. Convection should tend to wane and come to an end with loss of heating Thu night. Fri should tend to be more active convectively later in the day and Fri night as a cold front gains proximity. Will cap POPS in the chance category with a likelihood for greater thunderstorm coverage on Sat. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 300 PM Tuesday...Vertically stacked high pressure offshore will strengthen into Saturday ahead of a shortwave and associated cold front dropping into the OH VLY. The front will drop into the area and then likely stall as the shortwave hangs back, the front becomes flow-parallel, as ridging persists to the east. Convection chances will ramp up significantly Saturday, with still good chances Sunday as the shortwave digs through the Mid-Atlantic and offshore. Temps for the wknd will remain above climo as well. Concern then shifts to Monday, the day of the total solar eclipse. Guidance has backed off on a clean FROPA, and has the front dissipating overhead during Monday. This is much more typical for late August. While this could create more clouds and unsettled conditions for Monday across the area, mid-level flow does become W/NW behind the aforementioned shortwave which brings some drier air into the mid-levels. At this time a fairly typical August day is expected with aftn CU and convection, especially focused along the stalled boundary wherever that may set up. This does not suggest the eclipse will not be visible, but may be temporarily blocked by convection at times. On Tuesday offshore high pressure re-asserts itself, but yet another weak cold front will approach from the NW creating good convection chances with continuing above climo heat and humidity. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... As of 18Z...Potential for brief MVFR in any heavy downpours this afternoon/evening, as well as possible areas of MVFR with fog across the area Thursday morning. Otherwise expect VFR. Latest radar imagery remains fairly quiet at the terminals at this time, but just outside of the forecast area, showers are beginning to develop. Have kept VCTS/VCSH in the going forecast for all terminals through this evening. Any heavy downpours could create brief MVFR. Expect activity to deteriorate into the overnight hours. Towards the morning hours, patchy areas of fog may create MVFR, quickly dissipating after daybreak. Overall winds will remain light and variable through the period. Extended Outlook...A brief period of MVFR or lower conditions can not be ruled out in isolated to scattered showers and thunderstorms through Fri. The risk for flight restrictions due to showers and thunderstorms will increase significantly on Sat and Sun. Low stratus and some fog during the overnight and early morning hours may result in flight restrictions as well each day. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1015 AM Wednesday...As Hurricane Gert continues to move off to the northeast, well away from our waters, expect weak southwest flow this morning to become south-southeast this afternoon as the afternoon seabreeze develops. Winds will peak around 10 kts. Seas of 2 to 4 ft will continue to gradually drop throughout the day. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 300 AM Wednesday...A trough will wash out by/during Thu morning and the Piedmont Trough and Bermuda High will be in place for the balance of the forecast period. A cold front will approach the waters from the NW Fri night. Initially, the wind direction may be light E or SE with the direction veering to S Thu afternoon and SW Thu night. SW winds will then persist through the end of the period, increasing to 15 to 20 kt Fri afternoon and night. The strengthening winds will allow seas to build from 2 ft Thu and Thu night to 3 ft Fri afternoon and 3 to 4 ft Fri night. LONG TERM /SATURDAY THROUGH SUNDAY/... As of 300 PM Tuesday...A cold front approaching from the NW will sandwich the waters with a pinched gradient as high pressure spins offshore. This will result in SW winds of around 15 kt into Sunday morning. This front will stall and begin to dissipate inland from the waters on Sunday, causing the gradient to relax and wind speeds to fall to around 10 kt while maintaining a SW direction. Initially seas will be 2 to 4 ft, but will increase thanks to an amplifying SW wind wave, becoming 3-5 ft by Saturday night. Conditions should remain just below any cautionary statements. As the winds begin to ease Sunday, seas will follow, with wave heights falling to around 3 ft at the end of the period. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...Heat Advisory until 5 PM EDT this afternoon for SCZ017-023-024- 032-033-039-053>056. NC...Heat Advisory until 5 PM EDT this afternoon for NCZ099-109. MARINE...None. && $$ NEAR TERM...SGL SHORT TERM...RJD LONG TERM...JDW AVIATION...SGL

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